Key Laboratory of Luminescence Analysis and Molecular Sensing, Ministry of Education, College of Chemistry and Chemical Engineering, Southwest University, Chongqing 400715, China.
Anal Methods. 2021 May 6;13(17):2066-2074. doi: 10.1039/d1ay00281c.
In this contribution, 2D Ni/Fe MOF nanosheets were synthesized by a simple two-step ultrasound strategy at room temperature, i.e. the 2D Ni-MOF with a lamellar structure was first synthesized by the top-down ultrasonic assisted stripping route, followed by introducing Fe3+ ions as a metal node and terephthalic acid as an organic ligand to form 2D Ni/Fe MOF nanosheets that exhibited weak oxidase-like and strong peroxidase-like properties. Relative to that of the single metal Ni-MOF and Fe-MOF, the peroxidase-mimicking capability of the 2D Ni/Fe MOF nanosheets increased by over 14-fold and 3-fold, respectively. Reactive oxygen trials indicated that the 2D Ni/Fe MOF nanosheets can efficiently catalyze the decomposition of H2O2 to generate the ˙OH and O2˙- radicals, which can oxidize TMB to oxTMB from colorless to blue. The kinetic trial demonstrated the high affinity of the 2D Ni/Fe MOF nanosheet to H2O2 with a Km of 0.037 mM, which was 100 times lower than that of HRP. These impressive characteristics are likely related to the good dispersion of the in situ formed Fe MOF in the 2D Ni-MOF nanosheet structure with coordinatively unsaturated metal sites. This allows the 2D Ni/Fe MOF nanosheets to expose more active metal sites and to enhance the intrinsic catalytic activity of each site due to the synergistic interaction between the two metals. Interestingly, glutathione can obviously restrict the peroxidase-like activity of the 2D Ni/Fe MOF nanosheet, while the inhibited TMB oxidation can be restored upon further introducing Hg2+ ions due to the high and specific affinity of Hg2+ to thiol groups in glutathione. Based on the above facts, the 2D Ni/Fe MOF nanozyme was used to construct a nanoplatform to determine multiple targets, i.e. H2O2, glutathione and Hg2+. The 2D Ni/Fe MOF nanozyme-based colorimetric assay exhibits a linear response to H2O2, glutathione and Hg2+ ions over the 0.01-100 μM, 0.02-100 μM, and 100 nM to 200 μM ranges, respectively. The limits of detection (3σ) for the determination of H2O2, glutathione and Hg2+ are 10 nM, 10 nM, and 100 nM, respectively. This method was used to determinate the content of Hg2+ ions in real water samples.
在本研究中，通过一种简单的两步室温超声策略合成了二维 Ni/Fe MOF 纳米片，即首先通过自上而下的超声辅助剥离途径合成具有层状结构的二维 Ni-MOF，然后引入 Fe3+离子作为金属节点和对苯二甲酸作为有机配体，形成二维 Ni/Fe MOF 纳米片，其具有较弱的氧化酶样和较强的过氧化物酶样特性。与单一金属 Ni-MOF 和 Fe-MOF 相比，二维 Ni/Fe MOF 纳米片的过氧化物酶模拟能力分别提高了 14 倍和 3 倍。活性氧试验表明，二维 Ni/Fe MOF 纳米片可以有效地催化 H2O2 的分解，生成˙OH 和 O2˙-自由基，这些自由基可以将 TMB 氧化为蓝色的 oxTMB。动力学试验表明，二维 Ni/Fe MOF 纳米片对 H2O2 具有高亲和力，Km 值为 0.037 mM，比 HRP 低 100 倍。这些令人印象深刻的特性可能与原位形成的 Fe MOF 在二维 Ni-MOF 纳米片结构中良好的分散有关，其中具有配位不饱和金属位点。这使得二维 Ni/Fe MOF 纳米片能够暴露更多的活性金属位点，并由于两种金属之间的协同相互作用而增强每个位点的固有催化活性。有趣的是，谷胱甘肽可以明显限制二维 Ni/Fe MOF 纳米片的过氧化物酶样活性，而进一步引入 Hg2+离子可以恢复被抑制的 TMB 氧化，因为 Hg2+对谷胱甘肽中的巯基具有高特异性亲和力。基于上述事实，二维 Ni/Fe MOF 纳米酶被用于构建一种纳米平台来测定多个靶标，即 H2O2、谷胱甘肽和 Hg2+。基于二维 Ni/Fe MOF 纳米酶的比色测定法对 H2O2、谷胱甘肽和 Hg2+离子的线性响应范围分别为 0.01-100 μM、0.02-100 μM 和 100 nM 至 200 μM。测定 H2O2、谷胱甘肽和 Hg2+的检测限（3σ）分别为 10 nM、10 nM 和 100 nM。该方法用于测定实际水样中的 Hg2+离子含量。
